A seatback frame disclosed in Japanese Patent Application Laid-Open (JP-A) No. H7-303541 is a press-formed item of a single plate, and is provided with an outer periphery flange portion and a plural number of drawn flange portions formed by drawing machining. Each drawn flanged portion is disposed so as to linearly link a point of support of the seatback at a vehicle body side and a point of action of a forward load on the seatback. Thus, stiffness of the seatback frame is effectively improved.